there would have to be an agreement not to blindside me with "Hey, she's shinier; I'm leaving you!" Because I know mono is mono and might prefer a mono partner

This has been my issue in his crush/infatuation with this woman. Mono schooled me well in believing that if he turned his glance elsewhere it would mean the end of what we have. He said he would still be in my life, but as a friend. That was not okay with me and I always feared he would leave me for someone more suitable. Someone mono minded. He's mono, that's how it works.

He always said that what we have is perfect for him. I don't require huge amounts of his time, I leave him to his own devices as I have my own life going on with others and require a large amount for independence. I was challenged when she came into the picture. Especially as his crush had gone on for months and he never told me. She too felt the same it turned out. I still think she does and that is why she continues to write to him at interesting moments where I am particularly close to him... (As is evident on fb).

I thought we had an agreement of no blindsiding. Yet how does one go about not doing that. Its impossible in mono relationships when they end I think. Maybe if it ends before someone new comes along? That's the only way I can see that a mono relationship would end without one person being blind sided by their partner leaving them for another. Either you are in the relationship or not. There is no working in another partner together with them.

The two of them could not be together because she is married anyway. Another thing that makes me very nervous. Her marriage is struggling and he offers a way out to her I think. Even if its a fantasy of something different, exciting, new, more rewarding than what she has with her husband.

If he decided to be poly she would have to be part of my life and he would not want that. He doesn't think we would get along. He would have to choose if that is the case and I wonder sometimes if that is why he chooses not to take on poly with her. He could push it if she meant that much. Couldn't he?

If she didn't work out, maybe someone sometime will. He says not, because it was such a unique experience. Maybe he's right. There are a lot of complicated factors. Who knows.